<!DOCTYPE html>
<html lang="en"><head>
  <meta charset="utf-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1"><!-- Begin Jekyll SEO tag v2.8.0 -->
<title>0065: MVC X – TreeStore Basics | gtkDcoding</title>
<meta name="generator" content="Jekyll v4.3.4" />
<meta property="og:title" content="0065: MVC X – TreeStore Basics" />
<meta name="author" content="Ron Tarrant" />
<meta property="og:locale" content="en_US" />
<meta name="description" content="GTK Tutorial covering the basics of using a TreeStore." />
<meta property="og:description" content="GTK Tutorial covering the basics of using a TreeStore." />
<link rel="canonical" href="http://localhost:4000/posts/0065-mvc-x-treestore-basics.html" />
<meta property="og:url" content="http://localhost:4000/posts/0065-mvc-x-treestore-basics.html" />
<meta property="og:site_name" content="gtkDcoding" />
<meta property="og:type" content="article" />
<meta property="article:published_time" content="2019-08-27T00:00:00-04:00" />
<meta name="twitter:card" content="summary" />
<meta property="twitter:title" content="0065: MVC X – TreeStore Basics" />
<script type="application/ld+json">
{"@context":"https://schema.org","@type":"BlogPosting","author":{"@type":"Person","name":"Ron Tarrant"},"dateModified":"2019-08-27T00:00:00-04:00","datePublished":"2019-08-27T00:00:00-04:00","description":"GTK Tutorial covering the basics of using a TreeStore.","headline":"0065: MVC X – TreeStore Basics","mainEntityOfPage":{"@type":"WebPage","@id":"http://localhost:4000/posts/0065-mvc-x-treestore-basics.html"},"url":"http://localhost:4000/posts/0065-mvc-x-treestore-basics.html"}</script>
<!-- End Jekyll SEO tag -->
<link rel="stylesheet" href="../assets/main.css">
  <link rel="stylesheet" href="../css/style.css" /><link type="application/atom+xml" rel="alternate" href="http://localhost:4000/feed.xml" title="gtkDcoding" /></head>
<body><header class="site-header" role="banner">

  <div class="wrapper"><a class="site-title" rel="author" href="../">gtkDcoding</a><nav class="site-nav">
        <input type="checkbox" id="nav-trigger" class="nav-trigger" />
        <label for="nav-trigger">
          <span class="menu-icon">
            <svg viewBox="0 0 18 15" width="18px" height="15px">
              <path d="M18,1.484c0,0.82-0.665,1.484-1.484,1.484H1.484C0.665,2.969,0,2.304,0,1.484l0,0C0,0.665,0.665,0,1.484,0 h15.032C17.335,0,18,0.665,18,1.484L18,1.484z M18,7.516C18,8.335,17.335,9,16.516,9H1.484C0.665,9,0,8.335,0,7.516l0,0 c0-0.82,0.665-1.484,1.484-1.484h15.032C17.335,6.031,18,6.696,18,7.516L18,7.516z M18,13.516C18,14.335,17.335,15,16.516,15H1.484 C0.665,15,0,14.335,0,13.516l0,0c0-0.82,0.665-1.483,1.484-1.483h15.032C17.335,12.031,18,12.695,18,13.516L18,13.516z"/>
            </svg>
          </span>
        </label>

        <div class="trigger"><a class="page-link" href="../about.html">About</a><a class="page-link" href="../index-reverse.html">Posts in Date Order</a><a class="page-link" href="../topics.html">Blog Posts by Topic</a></div>
      </nav></div>
</header>
<main class="page-content" aria-label="Content">
      <div class="wrapper">
        <article class="post h-entry" itemscope itemtype="http://schema.org/BlogPosting">
	<header class="post-header">
		<link rel="stylesheet" href="../css/font_size.css" />
		<link rel="stylesheet" href="../css/figure.css" />
		<link rel="stylesheet" href="../css/topics/mvc.css" />  <!-- sub in the tag/topic -->
		<link rel="stylesheet" href="../css/modal.css" />
		<link rel="stylesheet" href="../css/post.css" />
		<link rel="stylesheet" href="../css/mascot_effects.css" />

		
		
		<p class="post-meta">
		<time class="dt-published" datetime="2019-08-27T00:00:00-04:00" itemprop="datePublished">Tuesday, August 27, 2019
		</time>• by <span itemprop="author" itemscope itemtype="http://schema.org/Person"><span class="p-author h-card" itemprop="name">Ron Tarrant</span></span></p>
	</header>

	<div class="post-content e-content" itemprop="articleBody">
		<div class="skew-line"></div>
		<h1 id="0065-mvc-x--treestore-basics">0065: MVC X – TreeStore Basics</h1>

<p>About a month ago, we broke away from <em>MVC</em> to talk about drawing with <em>Cairo</em>. Time to go back and pick up where we left off…</p>

<h2 id="treestore-modeling-with-append">TreeStore Modeling with append()</h2>

<!-- 0, 1 -->
<!-- first occurrence of application and terminal screen shots on a single page -->
<div class="screenshot-frame">
	<div class="frame-header">
		Results of this example:
	</div>
	<div class="frame-screenshot">
		<figure>
			<img id="img0" src="../images/screenshots/017_mvc/mvc_14.png" alt="Current example output" />		<!-- img# -->
			
			<!-- Modal for screenshot -->
			<div id="modal0" class="modal">																	<!-- modal# -->
				<span class="close0">&times;</span>															<!-- close# -->
				<img class="modal-content" id="img00" />															<!-- img## -->
				<div id="caption"></div>
			</div>
			
			<script>
			// Get the modal
			var modal = document.getElementById("modal0");														// modal#
			
			// Get the image and insert it inside the modal - use its "alt" text as a caption
			var img = document.getElementById("img0");															// img#
			var modalImg = document.getElementById("img00");													// img##
			var captionText = document.getElementById("caption");

			img.onclick = function()
			{
			  modal.style.display = "block";
			  modalImg.src = this.src;
			  captionText.innerHTML = this.alt;
			}
			
			// Get the <span> element that closes the modal
			var span = document.getElementsByClassName("close0")[0];											// close#
			
			// When the user clicks on <span> (x), close the modal
			span.onclick = function()
			{ 
				modal.style.display = "none";
			}
			</script>
			<figcaption>
			Current example output
			</figcaption>
		</figure>
	</div>

	<div class="frame-terminal">
		<figure class="right">
			<img id="img1" src="../images/screenshots/017_mvc/mvc_14_term.png" alt="Current example terminal output" />		<!-- img#, filename -->

			<!-- Modal for terminal shot -->
			<div id="modal1" class="modal">																				<!-- modal# -->
				<span class="close1">&times;</span>																		<!-- close# -->
				<img class="modal-content" id="img11" />																		<!-- img## -->
				<div id="caption"></div>
			</div>
			
			<script>
			// Get the modal
			var modal = document.getElementById("modal1");																	// modal#
			
			// Get the image and insert it inside the modal - use its "alt" text as a caption
			var img = document.getElementById("img1");																		// img#
			var modalImg = document.getElementById("img11");																// img##
			var captionText = document.getElementById("caption");

			img.onclick = function()
			{
			  modal.style.display = "block";
			  modalImg.src = this.src;
			  captionText.innerHTML = this.alt;
			}
			
			// Get the <span> element that closes the modal
			var span = document.getElementsByClassName("close1")[0];														// close#
			
			// When the user clicks on <span> (x), close the modal
			span.onclick = function()
			{ 
				modal.style.display = "none";
			}
			</script>

			<figcaption>
				Current example terminal output (click for enlarged view)
			</figcaption>
		</figure>
	</div>

	<div class="frame-footer">																								<!-- ------------- filename (below) --------- -->
		The code file for this example is available <a href="https://github.com/rontarrant/gtkd_demos/blob/master/017_mvc/mvc_14_treestore_append.d" target="_blank">here</a>.
	</div>
</div>
<!-- end of snippet for first (1st) occurrence of application and terminal screen shots on a single page -->

<p>As mentioned in <a href="./0048-mvc-i-introduction.html">the introduction to this series</a>, the <code class="language-plaintext highlighter-rouge">TreeStore</code> isn’t populated in quite the same way as a <code class="language-plaintext highlighter-rouge">ListStore</code> because a <code class="language-plaintext highlighter-rouge">ListStore</code> is a flat model while a <code class="language-plaintext highlighter-rouge">TreeStore</code> has a hierarchy.  But the difference isn’t that drastic.</p>

<p>In a flat model store, each row iter is created without associating it with any other, but in a hierarchical store, we do this:</p>

<ul>
  <li>create a row iter, and</li>
  <li>use that iter to create a child row iter.</li>
</ul>

<p>And if you add a grandchild row or even more generations, it’s the same process all the way down.</p>

<p>Of course, we also have to populate the rows as we go along, so we stuff this extra step in between the other two:</p>

<ul>
  <li>create a row iter,</li>
  <li>populate it,</li>
  <li>use the existing iter as a parent as we create and populate the child row.</li>
</ul>

<p>There are two approaches we can use, one with <code class="language-plaintext highlighter-rouge">append()</code> and <code class="language-plaintext highlighter-rouge">prepend()</code>, the other with <code class="language-plaintext highlighter-rouge">createIter()</code>, all of which are functions of the <code class="language-plaintext highlighter-rouge">TreeStore</code> object.</p>

<p>The code for a simple parent/child relationship might look like this:</p>

<div class="language-d highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="k">class</span> <span class="n">DemoTreeStore</span> <span class="p">:</span> <span class="n">TreeStore</span>
<span class="p">{</span>
	<span class="n">TreeIter</span> <span class="n">parentIter</span><span class="p">,</span> <span class="n">childIter</span><span class="p">;</span>
	<span class="nb">string</span> <span class="n">parentRowString</span> <span class="p">=</span> <span class="s">"Parent"</span><span class="p">;</span>
	<span class="nb">string</span> <span class="n">childRowString</span> <span class="p">=</span> <span class="s">"Child"</span><span class="p">;</span>
	 
	<span class="k">this</span><span class="p">()</span>
	<span class="p">{</span>
		<span class="k">super</span><span class="p">([</span><span class="n">GType</span><span class="p">.</span><span class="n">STRING</span><span class="p">,</span> <span class="n">GType</span><span class="p">.</span><span class="n">STRING</span><span class="p">]);</span>

		<span class="n">parentIter</span> <span class="p">=</span> <span class="n">append</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span>
		<span class="n">setValue</span><span class="p">(</span><span class="n">parentIter</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="n">parentRowString</span><span class="p">);</span>

		<span class="n">childIter</span> <span class="p">=</span> <span class="n">append</span><span class="p">(</span><span class="n">parentIter</span><span class="p">);</span>
		<span class="n">setValue</span><span class="p">(</span><span class="n">childIter</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="n">childRowString</span><span class="p">);</span>
		
	<span class="p">}</span> <span class="c1">// this()</span>
	
<span class="p">}</span> <span class="c1">// class DemoTreeStore</span>
</code></pre></div></div>

<p>The first step in the constructor is the same as any other store/model. The super-class constructor needs an array of types, one for each column.</p>

<p>But then we depart from the flat model procedure. Comparing the two calls to <code class="language-plaintext highlighter-rouge">append()</code>:</p>

<ul>
  <li>for the parent row, <code class="language-plaintext highlighter-rouge">append()</code> is passed a <code class="language-plaintext highlighter-rouge">null</code> value, but</li>
  <li>for the child row, <code class="language-plaintext highlighter-rouge">append()</code> is passed the parent row’s iter.</li>
</ul>

<p>The three bits of knowledge to glean from all this are:</p>

<ul>
  <li><code class="language-plaintext highlighter-rouge">append()</code> always returns a <code class="language-plaintext highlighter-rouge">TreeIter</code>,</li>
  <li>a <code class="language-plaintext highlighter-rouge">null</code> value tells <code class="language-plaintext highlighter-rouge">append()</code> to create a top-level row, and</li>
  <li>a non-<code class="language-plaintext highlighter-rouge">null</code> value tells <code class="language-plaintext highlighter-rouge">append()</code> that the row being created is a child.</li>
</ul>

<p>But, one thing we can’t do with <code class="language-plaintext highlighter-rouge">append(</code>) is populate the row, so we still need to do that with <code class="language-plaintext highlighter-rouge">setValue()</code>.</p>

<p>In effect, this approach allows us to use whatever <code class="language-plaintext highlighter-rouge">TreeIter</code> is returned by <code class="language-plaintext highlighter-rouge">append(</code>) to create the next generation of rows, going from parent to child to grandchild, etc.</p>

<h2 id="treestore-with-multiple-top-level-rows">TreeStore with Multiple Top-level Rows</h2>

<!-- 2, 3 -->
<!-- second occurrence of application and terminal screenshots on a single page -->
<div class="screenshot-frame">
	<div class="frame-header">
		Results of this example:
	</div>
	<div class="frame-screenshot">
		<figure>
			<img id="img2" src="../images/screenshots/017_mvc/mvc_15.png" alt="Current example output" />		<!-- img# -->
			
			<!-- Modal for screenshot -->
			<div id="modal2" class="modal">																<!-- modal# -->
				<span class="close2">&times;</span>														<!-- close# -->
				<img class="modal-content" id="img22" />														<!-- img## -->
				<div id="caption"></div>
			</div>
			
			<script>
			// Get the modal
			var modal = document.getElementById("modal2");													// modal#
			
			// Get the image and insert it inside the modal - use its "alt" text as a caption
			var img = document.getElementById("img2");														// img#
			var modalImg = document.getElementById("img22");												// img##
			var captionText = document.getElementById("caption");

			img.onclick = function()
			{
			  modal.style.display = "block";
			  modalImg.src = this.src;
			  captionText.innerHTML = this.alt;
			}
			
			// Get the <span> element that closes the modal
			var span = document.getElementsByClassName("close2")[0];										// close#
			
			// When the user clicks on <span> (x), close the modal
			span.onclick = function()
			{ 
				modal.style.display = "none";
			}
			</script>
			<figcaption>
			Current example output
			</figcaption>
		</figure>
	</div>

	<div class="frame-terminal">
		<figure class="right">
			<img id="img3" src="../images/screenshots/017_mvc/mvc_15_term.png" alt="Current example terminal output" /> 		<!-- img#, filename -->

			<!-- Modal for terminal shot -->
			<div id="modal3" class="modal">																			<!-- modal# -->
				<span class="close3">&times;</span>																	<!-- close# -->
				<img class="modal-content" id="img33" />																	<!-- img## -->
				<div id="caption"></div>
			</div>
			
			<script>
			// Get the modal
			var modal = document.getElementById("modal3");																// modal#
			
			// Get the image and insert it inside the modal - use its "alt" text as a caption
			var img = document.getElementById("img3");																	// img#
			var modalImg = document.getElementById("img33");															// img##
			var captionText = document.getElementById("caption");

			img.onclick = function()
			{
			  modal.style.display = "block";
			  modalImg.src = this.src;
			  captionText.innerHTML = this.alt;
			}
			
			// Get the <span> element that closes the modal
			var span = document.getElementsByClassName("close3")[0];													// close#
			
			// When the user clicks on <span> (x), close the modal
			span.onclick = function()
			{ 
				modal.style.display = "none";
			}
			</script>

			<figcaption>
				Current example terminal output (click for enlarged view)
			</figcaption>
		</figure>
	</div>

	<div class="frame-footer">																							<!--------- filename (below) ------------>
		The code file for this example is available <a href="https://github.com/rontarrant/gtkd_demos/blob/master/017_mvc/mvc_15_treestore_append_multiple.d" target="_blank">here</a>.
	</div>
</div>
<!-- end of snippet for second (2nd) occurrence of application and terminal screenshots on a single page -->

<p>For completeness sake, here’s a second example that adds multiple children to each of three top-level rows. The relevant code looks like this:</p>

<div class="language-d highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="k">this</span><span class="p">()</span>
<span class="p">{</span>
	<span class="k">super</span><span class="p">([</span><span class="n">GType</span><span class="p">.</span><span class="n">STRING</span><span class="p">,</span> <span class="n">GType</span><span class="p">.</span><span class="n">STRING</span><span class="p">]);</span>

	<span class="n">parentIter</span> <span class="p">=</span> <span class="n">append</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span> <span class="c1">// first header row</span>
	<span class="n">setValue</span><span class="p">(</span><span class="n">parentIter</span><span class="p">,</span> <span class="n">parentColumn</span><span class="p">,</span> <span class="s">"Mom #1"</span><span class="p">);</span>
	
	<span class="n">append</span><span class="p">(</span><span class="n">childIter</span><span class="p">,</span> <span class="n">parentIter</span><span class="p">);</span>
	<span class="n">setValue</span><span class="p">(</span><span class="n">childIter</span><span class="p">,</span> <span class="n">childColumn</span><span class="p">,</span> <span class="s">"Kid #1"</span><span class="p">);</span>
	<span class="n">append</span><span class="p">(</span><span class="n">childIter</span><span class="p">,</span> <span class="n">parentIter</span><span class="p">);</span>
	<span class="n">setValue</span><span class="p">(</span><span class="n">childIter</span><span class="p">,</span> <span class="n">childColumn</span><span class="p">,</span> <span class="s">"Kid #2"</span><span class="p">);</span>

	<span class="n">parentIter</span> <span class="p">=</span> <span class="n">append</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span> <span class="c1">// first header row</span>
	<span class="n">setValue</span><span class="p">(</span><span class="n">parentIter</span><span class="p">,</span> <span class="n">parentColumn</span><span class="p">,</span> <span class="s">"Dad #1"</span><span class="p">);</span>
	
	<span class="n">append</span><span class="p">(</span><span class="n">childIter</span><span class="p">,</span> <span class="n">parentIter</span><span class="p">);</span>
	<span class="n">setValue</span><span class="p">(</span><span class="n">childIter</span><span class="p">,</span> <span class="n">childColumn</span><span class="p">,</span> <span class="s">"Kid #3"</span><span class="p">);</span>
	<span class="n">append</span><span class="p">(</span><span class="n">childIter</span><span class="p">,</span> <span class="n">parentIter</span><span class="p">);</span>
	<span class="n">setValue</span><span class="p">(</span><span class="n">childIter</span><span class="p">,</span> <span class="n">childColumn</span><span class="p">,</span> <span class="s">"Kid #4"</span><span class="p">);</span>

	<span class="n">parentIter</span> <span class="p">=</span> <span class="n">append</span><span class="p">(</span><span class="kc">null</span><span class="p">);</span> <span class="c1">// first header row</span>
	<span class="n">setValue</span><span class="p">(</span><span class="n">parentIter</span><span class="p">,</span> <span class="n">parentColumn</span><span class="p">,</span> <span class="s">"Mom #2"</span><span class="p">);</span>
	
	<span class="n">append</span><span class="p">(</span><span class="n">childIter</span><span class="p">,</span> <span class="n">parentIter</span><span class="p">);</span>
	<span class="n">setValue</span><span class="p">(</span><span class="n">childIter</span><span class="p">,</span> <span class="n">childColumn</span><span class="p">,</span> <span class="s">"Kid #5"</span><span class="p">);</span>
	<span class="n">append</span><span class="p">(</span><span class="n">childIter</span><span class="p">,</span> <span class="n">parentIter</span><span class="p">);</span>
	<span class="n">setValue</span><span class="p">(</span><span class="n">childIter</span><span class="p">,</span> <span class="n">childColumn</span><span class="p">,</span> <span class="s">"Kid #6"</span><span class="p">);</span>
	<span class="n">append</span><span class="p">(</span><span class="n">childIter</span><span class="p">,</span> <span class="n">parentIter</span><span class="p">);</span>
	<span class="n">setValue</span><span class="p">(</span><span class="n">childIter</span><span class="p">,</span> <span class="n">childColumn</span><span class="p">,</span> <span class="s">"Kid #7"</span><span class="p">);</span>
	
<span class="p">}</span> <span class="c1">// this()</span>
</code></pre></div></div>

<p>This should be straightforward to work out… we’re appending a parent row followed by the children of that parent, then moving on to the next parent.</p>

<p>But I mentioned earlier that there’s a second way to do this, so let’s look at that…</p>

<h2 id="treestore-modeling-with-createiter">TreeStore Modeling with createIter()</h2>

<!-- 4, 5 -->
<!-- third occurrence of application and terminal screenshots on a single page -->
<div class="screenshot-frame">
	<div class="frame-header">
		Results of this example:
	</div>
	<div class="frame-screenshot">
		<figure>
			<img id="img4" src="../images/screenshots/017_mvc/mvc_16.png" alt="Current example output" />		<!-- img# -->
			
			<!-- Modal for screenshot -->
			<div id="modal4" class="modal">																<!-- modal# -->
				<span class="close4">&times;</span>														<!-- close# -->
				<img class="modal-content" id="img44" />														<!-- img## -->
				<div id="caption"></div>
			</div>
			
			<script>
			// Get the modal
			var modal = document.getElementById("modal4");													// modal#
			
			// Get the image and insert it inside the modal - use its "alt" text as a caption
			var img = document.getElementById("img4");														// img#
			var modalImg = document.getElementById("img44");												// img##
			var captionText = document.getElementById("caption");

			img.onclick = function()
			{
			  modal.style.display = "block";
			  modalImg.src = this.src;
			  captionText.innerHTML = this.alt;
			}
			
			// Get the <span> element that closes the modal
			var span = document.getElementsByClassName("close4")[0];										// close#
			
			// When the user clicks on <span> (x), close the modal
			span.onclick = function()
			{ 
				modal.style.display = "none";
			}
			</script>
			<figcaption>
			Current example output
			</figcaption>
		</figure>
	</div>

	<div class="frame-terminal">
		<figure class="right">
			<img id="img5" src="../images/screenshots/017_mvc/mvc_16_term.png" alt="Current example terminal output" /> 		<!-- img#, filename -->

			<!-- Modal for terminal shot -->
			<div id="modal5" class="modal">																			<!-- modal# -->
				<span class="close5">&times;</span>																	<!-- close# -->
				<img class="modal-content" id="img55" />																	<!-- img## -->
				<div id="caption"></div>
			</div>
			
			<script>
			// Get the modal
			var modal = document.getElementById("modal5");																// modal#
			
			// Get the image and insert it inside the modal - use its "alt" text as a caption
			var img = document.getElementById("img5");																	// img#
			var modalImg = document.getElementById("img55");															// img##
			var captionText = document.getElementById("caption");

			img.onclick = function()
			{
			  modal.style.display = "block";
			  modalImg.src = this.src;
			  captionText.innerHTML = this.alt;
			}
			
			// Get the <span> element that closes the modal
			var span = document.getElementsByClassName("close5")[0];													// close#
			
			// When the user clicks on <span> (x), close the modal
			span.onclick = function()
			{ 
				modal.style.display = "none";
			}
			</script>

			<figcaption>
				Current example terminal output (click for enlarged view)
			</figcaption>
		</figure>
	</div>

	<div class="frame-footer">																							<!---------- filename (below) ---------->
		The code file for this example is available <a href="https://github.com/rontarrant/gtkd_demos/blob/master/017_mvc/mvc_16_treestore_createiter.d" target="_blank">here</a>.
	</div>
</div>
<!-- end of snippet for third (3rd) occurrence of application and terminal screenshots on a single page -->

<p>The main difference here is that <code class="language-plaintext highlighter-rouge">createIter()</code> doesn’t need a null to know it’s creating a top-level row. Have a look:</p>

<div class="language-d highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="k">class</span> <span class="n">DemoTreeStore</span> <span class="p">:</span> <span class="n">TreeStore</span>
<span class="p">{</span>
	<span class="n">TreeIter</span> <span class="n">parentIter</span><span class="p">,</span> <span class="n">childIter</span><span class="p">;</span>
	<span class="nb">string</span> <span class="n">parentRowString</span> <span class="p">=</span> <span class="s">"Parent"</span><span class="p">;</span>
	<span class="nb">string</span> <span class="n">childRowString</span> <span class="p">=</span> <span class="s">"Child"</span><span class="p">;</span>
	 
	<span class="k">this</span><span class="p">()</span>
	<span class="p">{</span>
		<span class="k">super</span><span class="p">([</span><span class="n">GType</span><span class="p">.</span><span class="n">STRING</span><span class="p">,</span> <span class="n">GType</span><span class="p">.</span><span class="n">STRING</span><span class="p">]);</span>

		<span class="n">parentIter</span> <span class="p">=</span> <span class="n">createIter</span><span class="p">();</span>
		<span class="n">setValue</span><span class="p">(</span><span class="n">parentIter</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="n">parentRowString</span><span class="p">);</span>

		<span class="n">childIter</span> <span class="p">=</span> <span class="n">createIter</span><span class="p">(</span><span class="n">parentIter</span><span class="p">);</span>
		<span class="n">setValue</span><span class="p">(</span><span class="n">childIter</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="n">childRowString</span><span class="p">);</span>
		
	<span class="p">}</span> <span class="c1">// this()</span>
	
<span class="p">}</span> <span class="c1">// class DemoTreeStore</span>
</code></pre></div></div>

<p>Everything else is the same with just that simple substitution. <code class="language-plaintext highlighter-rouge">append()</code> becomes <code class="language-plaintext highlighter-rouge">creatIter()</code>, but the <code class="language-plaintext highlighter-rouge">createIter()</code> argument is either the parent iter or nothing at all.</p>

<h2 id="populating-a-treestore-in-a-loop-with-createiter">Populating a TreeStore in a Loop with createIter()</h2>

<!-- 6, 7 -->
<!-- third occurrence of application and terminal screenshots on a single page -->
<div class="screenshot-frame">
	<div class="frame-header">
		Results of this example:
	</div>
	<div class="frame-screenshot">
		<figure>
			<img id="img6" src="../images/screenshots/017_mvc/mvc_17.png" alt="Current example output" />		<!-- img# -->
			
			<!-- Modal for screenshot -->
			<div id="modal6" class="modal">																<!-- modal# -->
				<span class="close6">&times;</span>														<!-- close# -->
				<img class="modal-content" id="img66" />														<!-- img## -->
				<div id="caption"></div>
			</div>
			
			<script>
			// Get the modal
			var modal = document.getElementById("modal6");													// modal#
			
			// Get the image and insert it inside the modal - use its "alt" text as a caption
			var img = document.getElementById("img6");														// img#
			var modalImg = document.getElementById("img66");												// img##
			var captionText = document.getElementById("caption");

			img.onclick = function()
			{
			  modal.style.display = "block";
			  modalImg.src = this.src;
			  captionText.innerHTML = this.alt;
			}
			
			// Get the <span> element that closes the modal
			var span = document.getElementsByClassName("close6")[0];										// close#
			
			// When the user clicks on <span> (x), close the modal
			span.onclick = function()
			{ 
				modal.style.display = "none";
			}
			</script>
			<figcaption>
			Current example output
			</figcaption>
		</figure>
	</div>

	<div class="frame-terminal">
		<figure class="right">
			<img id="img7" src="../images/screenshots/017_mvc/mvc_17_term.png" alt="Current example terminal output" /> 		<!-- img#, filename -->

			<!-- Modal for terminal shot -->
			<div id="modal7" class="modal">																			<!-- modal# -->
				<span class="close7">&times;</span>																	<!-- close# -->
				<img class="modal-content" id="img77" />																	<!-- img## -->
				<div id="caption"></div>
			</div>
			
			<script>
			// Get the modal
			var modal = document.getElementById("modal7");																// modal#
			
			// Get the image and insert it inside the modal - use its "alt" text as a caption
			var img = document.getElementById("img7");																	// img#
			var modalImg = document.getElementById("img77");															// img##
			var captionText = document.getElementById("caption");

			img.onclick = function()
			{
			  modal.style.display = "block";
			  modalImg.src = this.src;
			  captionText.innerHTML = this.alt;
			}
			
			// Get the <span> element that closes the modal
			var span = document.getElementsByClassName("close7")[0];													// close#
			
			// When the user clicks on <span> (x), close the modal
			span.onclick = function()
			{ 
				modal.style.display = "none";
			}
			</script>

			<figcaption>
				Current example terminal output (click for enlarged view)
			</figcaption>
		</figure>
	</div>

	<div class="frame-footer">																							<!---------- filename (below) ---------->
		The code file for this example is available <a href="https://github.com/rontarrant/gtkd_demos/blob/master/017_mvc/mvc_17_treestore_createiter_loop_fill.d" target="_blank">here</a>.
	</div>
</div>
<!-- end of snippet for fourth (4th) occurrence of application and terminal screen shots on a single page -->

<p>One last example today and it uses <code class="language-plaintext highlighter-rouge">createIter()</code> as we just did, but takes what we did with the multiple top-level rows example and shoves it into a <code class="language-plaintext highlighter-rouge">foreach()</code> loop. Relevant code:</p>

<div class="language-d highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="k">this</span><span class="p">()</span>
<span class="p">{</span>
	<span class="k">super</span><span class="p">([</span><span class="n">GType</span><span class="p">.</span><span class="n">STRING</span><span class="p">,</span> <span class="n">GType</span><span class="p">.</span><span class="n">STRING</span><span class="p">]);</span>

	<span class="k">foreach</span><span class="p">(</span><span class="kt">ulong</span> <span class="n">i</span><span class="p">;</span> <span class="mf">0.</span><span class="p">.</span><span class="n">parentHeaders</span><span class="p">.</span><span class="n">length</span><span class="p">)</span>
	<span class="p">{</span>
		<span class="nb">string</span> <span class="n">parentTitle</span> <span class="p">=</span> <span class="n">parentHeaders</span><span class="p">[</span><span class="n">i</span><span class="p">];</span>
		<span class="nb">string</span><span class="p">[]</span> <span class="n">childFamily</span> <span class="p">=</span> <span class="n">children</span><span class="p">[</span><span class="n">i</span><span class="p">];</span>

		<span class="n">parentIter</span> <span class="p">=</span> <span class="n">createIter</span><span class="p">();</span> <span class="c1">// append an empty row to the top level and get an iter back</span>
		<span class="n">setValue</span><span class="p">(</span><span class="n">parentIter</span><span class="p">,</span> <span class="mi">0</span><span class="p">,</span> <span class="n">parentTitle</span><span class="p">);</span>

		<span class="k">foreach</span><span class="p">(</span><span class="kt">ulong</span> <span class="n">j</span><span class="p">;</span> <span class="mf">0.</span><span class="p">.</span><span class="n">childFamily</span><span class="p">.</span><span class="n">length</span><span class="p">)</span>
		<span class="p">{</span>
			<span class="n">childIter</span> <span class="p">=</span> <span class="n">createIter</span><span class="p">(</span><span class="n">parentIter</span><span class="p">);</span> <span class="c1">// passing in parentIter makes this a child row</span>

			<span class="nb">string</span> <span class="n">child</span> <span class="p">=</span> <span class="n">children</span><span class="p">[</span><span class="n">i</span><span class="p">][</span><span class="n">j</span><span class="p">];</span>
			<span class="n">setValue</span><span class="p">(</span><span class="n">childIter</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> <span class="n">child</span><span class="p">);</span>
		
		<span class="p">}</span>
	<span class="p">}</span>
	
<span class="p">}</span> <span class="c1">// this()</span>
</code></pre></div></div>

<p>No real surprises here. In the outside <code class="language-plaintext highlighter-rouge">foreach()</code> loop…</p>

<ul>
  <li>the parent iter is created as an empty row,</li>
  <li>its label is populated with <code class="language-plaintext highlighter-rouge">setValue()</code>,</li>
  <li>then the inner <code class="language-plaintext highlighter-rouge">foreach()</code> loop:
    <ul>
      <li>creates the <code class="language-plaintext highlighter-rouge">childIter</code> by passing in <code class="language-plaintext highlighter-rouge">parentIter</code>,</li>
      <li>picks the appropriate string from the <code class="language-plaintext highlighter-rouge">children</code> array, and</li>
      <li>does a <code class="language-plaintext highlighter-rouge">setValue()</code> to fill in the child rows.</li>
    </ul>
  </li>
</ul>

<h2 id="conclusion">Conclusion</h2>

<p>And that’s the basics of the <code class="language-plaintext highlighter-rouge">TreeStore</code> class.</p>

<div class="blog-nav">
	<div style="float: left;">
		<a href="./0064-cairo-vii-drawingarea-animation.html">Previous: Cairo DrawingArea Animation</a>
	</div>
	<div style="float: right;">
		<a href="./0066-toolbar-basics.html">Next: Toolbar Basics</a>
	</div>
</div>
<p>
	<h3></h3>
<div class="inpage-frame">
	<a href="https://github.com/sponsors/rontarrant">
		<BR>
		<BR>
		<B>Is this article useful? Educational? Entertaining, perhaps?</B>
		<BR>
		<figure class="left">
			<img src="../images/favorite_32.png" alt="Sponsorship heart" style="width: 32px; height: 32px;">
		</figure>
		You're free to accept or decline this invitation to become our newest sponsor.
	</a>
</div>
	<h4 class="comment-blurb"><B>Comments? Questions? Observations?</B></h4>
	<p>
		Did we miss a tidbit of information that would make this post even more informative? Let's talk about it in the comments.
	</p>
	<script src="https://utteranc.es/client.js"
		repo="rontarrant"
		issue-term="pathname"
		theme="github-light"
		crossorigin="anonymous"
		async>
	</script>
	<ul>
		<li> come on over to the <a href="https://forum.dlang.org/">D Language Forum</a> and look for one of the <i>gtkDcoding</i> announcement posts, </li>
		<li> drop by <a href="https://forum.gtkd.org/">the <i>GtkD Forum</i></a>,</li>
		<li> follow the link below to email me, or</li>
		<li> go to the	<a href="https://www.facebook.com">gtkDcoding Facebook page.</a></li>
	</ul>
</p>
<p> You can also subscribe <a href="/feed.xml">via RSS</a> so you won't miss anything. Thank you very much for dropping by.</p>
<p>&copy; Copyright 2025 Ron Tarrant </p>
</div>

	<a class="u-url" href="./0065-mvc-x-treestore-basics.html" hidden></a>
</article>

      </div>
    </main><footer class="site-footer h-card">
  <data class="u-url" href="/"></data>

  <div class="wrapper">

    <h2 class="footer-heading">gtkDcoding</h2>

    <div class="footer-col-wrapper">
      <div class="footer-col footer-col-1">
        <ul class="contact-list">
          <li class="p-name">Ron Tarrant</li><li><a class="u-email" href="mailto:gtkDcoding@gmail.com">gtkDcoding@gmail.com</a></li></ul>
      </div>

      <div class="footer-col footer-col-2"><ul class="social-media-list"><li><a href="https://github.com/rontarrant"><svg class="svg-icon"><use xlink:href="../assets/minima-social-icons.svg#github"></use></svg> <span class="username">rontarrant</span></a></li></ul>
</div>

      <div class="footer-col footer-col-3">
        <p>Simple examples of how to use GtkD to build GUI applications.</p>
      </div>
    </div>

  </div>

</footer>
</body>

</html>
